Concrete grinder



Feb. 2l, 1956 H. p BROWN 2,735,244

CONCRETE GRINDER Filed June l5, 1955 7T 9 2. L"""Nl 1N VENTOR Hlro uf n Y man ATTORNEY CONCRETE GRINDER Howard P. Brown, Columbus, Miss.

Application June 15, 1955, Serial No. 515,721

Claims. (Cl. 51-209) This invention relates to an improved grinder primarily adapted for wet grinding hard concrete to produce a stone finish.

In the wet grinding of hard concrete to produce a stone finish, the concrete must be kept wet with water until the grinding operation is completed, that is, until the glaze surface of the concrete is broken. The mortar which is thus ground off the concrete is then evenly spread over the ground surface and allowed to dry. 1f this mortar is thrown off from the surface or lost in any manner during the grinding operation, the ground concrete surface will not possess an even smooth stone-like finish.

Accordingly, it is a primary object of the present in vention to provide a grinder head for supporting therebeneath a plurality of grinding blocks of a particular construction supported in a particular relationship to the axis of the head whereby the wet mortar removed from the concrete surface by the grinding blocks will always be displaced toward the center of the head and so as to be spread by the grinding blocks as the grinder is moved to positions over different parts of the concrete surface.

Another object of the invention is to provide a rotary grinder wherein the grinding blocks or stones are supported in a spaced apart relation to one another such as to minimize heating of the concrete.

Another object of the invention is to provide a grinder having a diameter substantially greater than the thickness or depth thereof to provide a proper balance for the grinder while in use.

Still another object of the invention is to provide a grinder head having means for supporting a plurality of grinding blocks or stones so that the grinding operation can be accomplished more rapidly and smoothly.

Various other objects and advantages of the invention will hereinafter become more fully apparent from the following description of the drawing, illustrating a presently preferred embodiment thereof, and wherein:

Figure 1 is a side elevational view of the grinderin an operative position;

Figure 2 is an enlarged bottom plan view thereof, and

Figure 3 is a vertical sectional view on a reduced scale taken centrally through the grinder, substantially along a plane as indicated by the line 3 3 of Figure 2.

Referring more specifically to the drawing, the grinder in its entirety and comprising the invention is designated generally 5 and includes a head, designated generally 6, and four corresponding grinding blocks or stones, each designated generally 7.

The head 6 is substantially disk-shaped, as best seen in Figure 2, and the upper side of the central portion thereof is thickened, as best seen in Figure 3, to form a hub 8 having a central opening 9 adapted to receive an end portion of a rotary driven shaft 10 which may constitute a part of any suitable portable unit or power source 11. The shaft 10 is preferably provided with a Patented Feb. 21, 1956 rice fixed collar 12 which bears against the upper side of the hub 8 and its distal end or lower extremity 13 is preferably threaded to receive a nut 14 which engages against the underside of the hub 8 to secure the head 6 on the shaft 10 for rotation therewith.

The underside 15 of the head 6 is provided with four equally spaced projections each of which constitutes an angular lug or rib. Said lugs or ribs are designated generally 16, 17, 18 and 19. Said lugs or ribs are of identical construction and each includes an inner substantially straight arm 20 the axis of which is disposed substantially parallel to a tangent of the head 6 and relatively near the center of the head. The other substantially straight outer arm 21 of each lug or rib is disposed with its axis more remote from the center of the head 6. The inner edge 22 of each outer arm 21 is disposed at an angle of slightly greater than to the axis of the inner arm 20 of the same lug or rib. The outer longitudinal edges 23 of the arms 20 are disposed parallel to the axes of said arms. Thus, the edges 22 and 23 of adjacent arms 20 and 21 of different lugs or ribs, as for example the lugs 19 and 16, respectively, are disposed in inwardly converging relation to one another, as clearly illustrated in Figure 3.

The grinding stones or blocks 7 each have substantially flat top and bottom surfaces 24 and 25, respectively, substantially flat parallel side walls 26 and substantially flat parallel end walls 27. The top'and bottom surfaces 24 and 25 are rectangular, as seen in Figure 2, and each end Wall 27 is disposed at an acute angle to a side Wall 26 so that the top and bottom surfaces 24 and 25 have corners forming the ends thereof, as seen at 28, which define angles of substantially less than 90.

The grinding stones or blocks 7 are disposed with their top surfaces 24 abutting the flat underside 15 of the head 6 between the adjacent substantially opposed edges 23 and 22 of the arms4 20 and 21, respectively, of the four lugs, and with a portion of one side wall 26 0f each block or stone abutting flush against an edge 23, so that the other side wall 26 of the block 7 will be disposed at a slight angle to the edge 22 and in an outwardly converging relation relative thereto, as seen in Figure 2.

The blocks or stones 7 are detachably clamped in a position against the underside of the head 6 by relatively long slightly tapered wedges 29 which are driven into the spaces between the lug edges 22 andthe block walls` 26, located adjacent thereto, and toward the arm 20 forming a part of the same lug as the arm 21 which is engaged by the wedge.

It will thus be seen that when the grinding blocks or stones 7 are thus clamped against the underside 15 of the head 6, that the outer tips 28 of the grinding blocks will be located adjacent the apexes of the lugs and nearer the periphery of the head 6 than the other inner ends 28 which engage portions of the wedges 29. The outer end walls 27 which extend to said outer tips 28 each form an angle with a radius line running through the tip of less than 90 and are each disposed at such an angle as to approach the center of the head and recede from an adjacent portion of the periphery thereof from the outer tip 28 toward the adjacent wedge 29. The grinder 5 is revolved with the shaft 10 in a counterclockwise direction, as seen in Figure 2, so that the walls 26 of the blocks 7 which engage the edges 23 constitute the leading sides of the grinding blocks.

The grinder 5 is shown in Figures 1 and 3 in an opera.- tive position with the blocks 7 disposed beneath the head 6 and with the bottom surfaces 25 thereof engaging a concrete surface 30 to be ground for removing the glaze therefrom and which, it will be understood, is to be kept wet during the grinding operation. It will be readily apparent that the outer tips or ends 28 of the bottom 2,736,244 K t i surfaces 2S will described a circle larger than the circle described by any other portion of the surfaces 25. Ac-

cordingly, the material which is ground from the surface 30 and the water which is mixed therewith to form a mortar will be deflected by the leading walls 26 of the blocks 7 inwardly and toward the center of the grinder 5 so that none of such mortar, not shown, will be thrown outwardly by the grinding blocks. As the grinder is moved over the surface 30, translationally with respect thereto, the loose mortar disposed between the grinding blocks will be spread by the grinding surfaces to leave a smooth surface on the concrete face which when dry will have a stone-like finish or appearance.

Due to the gaps between the grinding surfaces 25 of the different blocks 7, the grinder 5 will not heat the concrete 30 to any appreciable extent during the grinding operation as frequently occurs where the grinding is accomplished by a substantially uninterrupted grinding surface. As seen in Figures 1 and 3, the diameter of the grinder 5 is substantially greater than its height or thickness which provides a good balance enabling the grinder to be held steady during the grinding operation and so that the grinding surfaces 25 will be disposed iiush against the concrete face 30. The head 6 may be formed of a lightweight metal, such as aluminum, to minimize the manual labor involved in the operation of the grinder. The longitudinal axes of the grinding faces 25 are disposed substantially parallel to tangents of the grinder S so that said surfaces will most eiectively` grind the surface 30.

Various modifications and changes are contemplated and may obviously be resorted to, Without departing from the spirit or scope of the invention as hereinafter defined by the appended claims.

I claim as my invention:

l. A grinder of the character described comprising a disk-shaped head having a central portion adapted to be secured to a rotary driving means for imparting rotation to the head, said head having a substantially iiat underside provided with four equally spaced depending projections deiining angular lugs each including an inner arm and an outer arm, the axes of said inner arms being disposed substantially parallel to tangents of the head and being located nearer the center of the head than the axes of said outer arms, the outer longitudinal edge of the inner arm of each lug being disposed at an obtuse angle to the inner longitudinal edge of the outer arm of said lug, grinding blocks having substantially at top surfaces disposed against the underside of the head, said blocks having substantially parallel side walls each including a first side wall having a portion abutting against an outer edge of an inner lug arm and a second side wall having a portion spaced from the inner longitudinal edge of an outer arm of an adjacent lug and disposed in inwardly converging relation thereto toward the other inner arm of said last mentioned lug, and Wedges engaging between said second side walls and said outer arms for detachably securing the blocks between said lugs, said blocks having substantially iiat bottom surfaces disposed below the level of the undersides of said lugs and wedges and adapted to engage a concrete surface to be ground.

2. A grinder as in claim 1, each of said blocks having an outer end wall disposed at an angle to the iirst side wall of substantially less than and such that a portion of said first side wall is located at a greater distance from the center of the head than said outer end wall.

3. A grinder as in claim 2, the top and bottom surfaces of saidblocks being substantially rectangular and each including a second end Wall disposed substantially parallel to said outer end wall.

4. A grinder of the character` described comprising a rotary driven disk-shaped head having a substantially at underside provided with four depending projections forming lugs, said lugs being disposed in corresponding spaced apart relation to one anotheriand each including an inner arm and an outer arm, the axes of said inner arms being disposed nearer the center of the head than the axes of said outer arms, the outer longitudinal edge of the inner arm of each lug being disposed at an obtuse angle to the inner longitudinal edge of the outer arm of said lug, grinding blocks having substantially dat top surfaces bearing against the underside of the head and including front walls having portions bearing against said outer edges of the inner arms and rear walls having portions spaced from said inner edges of the outer arms and disposed in inwardly converging relation thereto, and wedges disposed between said rear walls and said outer arms for detachably securing the blocks to the underside of the head, said blocks being thicker than the lugs and having substantially flat undersides adapted to engage a surface to be ground.

5. A grinder as in` claim 4, said blocks each having an outer yend wall forming an angle of substantially less than 90 with the front wall such that said outer end wall is disposed nearer the axis; ofthe head than the outer portion of the front wall, said front walls of thel blocks'constituting the leading sides thereof when the grinder is rotated.

No references cited. 

